Color-filter substrate, method and apparatus for manufacturing color-filter substrate, and liquid crystal display and method for manufacturing liquid crystal display

ABSTRACT

To make it difficult to view streak unevenness in alignment generated at the boundary of alignment layers even when an alignment-layer material is applied onto a color-filter substrate several times to form an alignment layer. When an alignment-layer material is applied onto a color-filter substrate  1  having color filters (R, G, and B) on the surface with a droplet discharge head  3  to form an alignment-layer train  4   a , the lateral front end L 1  of the train  4   a  is formed on the color filter (B) displaying blue. When the alignment-layer material is then applied to the following alignment-layer application train to form an alignment-layer train  4   b , the lateral rear end L 2  of the train  4   b  is overlapped with the lateral front end L 1  of the preceding alignment-layer train  4   a  to form an overlapped portion  4   c . Since the overlapped portion  4   c  is formed on the color filter (B) displaying blue which has the lowest visibility of the three primary colors of light, streak unevenness in alignment generated at the boundary is difficult to view from the exterior.

This is a Division of application Ser. No. 10/930,956 filed Sep. 1,2004. The disclosure of the prior application is incorporated byreference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a color-filter substrate having analignment layer divided in multiple alignment layer trains formed on acolor filter, a method and an apparatus for manufacturing thecolor-filter substrate, a liquid crystal device, and a method formanufacturing the liquid crystal device.

2. Description of Related Art

Liquid crystal devices have been recently broadly used for displays ofelectronic equipment including cellular phones, portable computers,video cameras, projectors, etc. This type of liquid crystal devicecontains liquid crystal sealed between a pair of substrates and controlsthe state of the alignment of the liquid crystal by an electric fieldapplied to the liquid crystal, thereby displaying images. Accordingly,liquid crystal devices have alignment layers on each of opposingsurfaces of a pair of substrates, and control the state of the alignmentof the liquid crystal under no electric field by the controlling forceof the alignment layers. For color display in liquid crystal devices, acolor filter layer is disposed under the alignment layer of onesubstrate.

Although flexography is well known as a method for forming an alignmentlayer on each substrate, a so-called droplet discharge method of formingan alignment layer on a substrate with a droplet discharge head has beenrecently proposed as a method of providing a relatively stable qualityas compared with the flexography.

For example, a technique of forming a pattern by discharging a minuteviscous material onto a substrate with an inkjet printer head has beendisclosed.

SUMMARY OF THE INVENTION

When the width of an alignment-layer application area on a substrate islarger than the width of a droplet discharge head, the droplet dischargehead must be moved to and fro to apply an alignment-layer material tothe alignment-layer application area of the substrate several times.

In that case, when the alignment-layer material is applied to the nexttrain following the application to the preceding train, thealignment-layer material on the preceding train has already been driedand solidified or being dried and solidified. Accordingly, the end ofthe alignment-layer material on the next train is overlapped with thealignment layer formed by the application of the alignment-layermaterial to the preceding train to eliminate the boundary of thealignment layers.

However, the alignment-layer overlapped portion becomes different inthickness from the other parts, causing unevenness in thickness. Theuneven alignment layer tends to affect the pre-tilt angle of liquidcrystal, which can be viewed as streak unevenness in alignment.

Accordingly, in view of the above-described problem, the presentinvention is directed to a color-filter substrate in which, even when analignment-layer material is applied several times, streak unevenness inalignment generated at the boundary thereof is difficult to see from theexterior to improve the quality of products, a method and an apparatusfor manufacturing the color filter, a liquid crystal device, and amethod for manufacturing the liquid crystal device.

In order to achieve the above object, according to a first invention,there is provided a color-filter substrate having an alignment layer ona plurality of color filters, wherein the alignment layer divided in aplurality of alignment layer trains is formed on the color filters, theadjacent ends of the alignment layer trains are overlapped with eachother to form an overlapped portion, and the overlapped portion isformed on a position corresponding to a color filter displaying aspecific color.

Since the structure is constructed such that the overlapped portion ofthe alignment layer train is formed at a position corresponding to acolor filter displaying a specific color, it is difficult to viewunevenness in alignment generated by the overlapped portion from theexterior.

A second invention is characterized in that the overlap width of theoverlapped portion is set within the color filter displaying a specificcolor in the first invention.

Since the structure is constructed such that the overlap width of theoverlapped portion is set within the color filter displaying a specificcolor, it is more difficult to view unevenness in alignment.

A third invention is characterized in that the specific color is blue inthe first or second invention.

Since the structure is constructed such that the specific color is bluewhich has relatively low visibility, the visibility of unevenness inalignment can be decreased more.

According to a fourth invention, there is provided a method formanufacturing a color-filter substrate by applying an alignment-layermaterial on a plurality of color filters to form an alignment layer, themethod comprising the steps of: applying the alignment-layer materialalong a preset alignment-layer application train such that the lateralfront end of the train corresponds to the position of a color filterdisplaying a specific color; and applying the alignment-layer materialalong the following alignment-layer application train such that thelateral rear end of the train overlaps with the front end of thealignment layer applied to the preceding alignment-layer applicationtrain and the lateral front end of the train is located at a positioncorresponding to the color filter displaying a specific color.

Since the structure is constructed such that the overlap width of theoverlapped portion is placed at a position corresponding to the colorfilter displaying a specific color, manufacture is facilitated andatomization is promoted.

A fifth invention is characterized in that the overlap width of theoverlapped portion is set within the color filter displaying a specificcolor in the fourth invention.

Since the structure is constructed such that the overlap width of theoverlapped portion is set within the color filter displaying a specificcolor, unevenness in alignment is more difficult to view.

A sixth invention is characterized in that the alignment-layer materialis applied onto the color filters with a droplet discharge head in theforth or fifth invention.

Since the structure is constructed such that the alignment-layermaterial is applied with a droplet discharge head, the thickness of thealignment layer is constant, thus providing a stable quality.

A seventh invention is characterized in that the alignment-layermaterial is applied onto the color filters by flexography in the fourthor fifth invention.

Since the structure is constructed such that the alignment-layermaterial is applied by flexography, the time for manufacture can bedecreased.

An eighth invention is characterized in that the specific color is bluein the fourth to seventh inventions.

Since the structure is constructed such that the specific color is bluewhich has relatively low visibility, the visibility of unevenness inalignment can be further decreased.

A ninth invention is characterized by comprising a table for placing asubstrate having a plurality of color filters, a droplet discharge headopposed to the substrate and capable of relative movement intwo-dimensional directions along the substrate, and a controller forcontrolling the two-dimensional relative movement of the table and thedroplet discharge head, wherein an alignment-layer material dischargedfrom nozzles provided to the droplet discharge head is applied along apreset alignment-layer application train by the relative movement of thesubstrate and the droplet discharge head such that the lateral front endof the train is located at a position corresponding to a color filterdisplaying a specific color; and the alignment-layer material is appliedalong the following alignment-layer application train such that thelateral rear end of the train is overlapped with the front end of thealignment layer applied to the preceding alignment-layer applicationtrain and the lateral front end is located at a position correspondingto the color filter displaying a specific color.

Since the structure is constructed such that the overlapped portion ofthe alignment layer is set to a position corresponding to a color filterdisplaying a specific color in manufacturing a color-filter substrate,manufacture is facilitated and atomization is promoted.

A tenth invention is characterized in that the specific color is blue inthe ninth invention.

Since the structure is constructed such that the specific color is bluewhich has relatively low visibility, the visibility of unevenness inalignment can be further decreased.

According to the present invention, even when an alignment-layermaterial is applied several times, streak unevenness in alignmentgenerated at the boundary thereof is difficult to see from the exterior,thus improving the quality of products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a color-filter substrate according to anembodiment of the present invention;

FIG. 2 is a cross-sectional view of the same, taken along line II-II ofFIG. 1;

FIG. 3 is a perspective view of the state in which an alignment-layermaterial is applied onto a color filter with a droplet discharge head;

FIG. 4 is an enlarged cross-sectional view of an essential part of thesame, showing the state in which an alignment-layer material is appliedon the color filter;

FIG. 5 is a plan view of the arrangement of color filters disposed onthe color-filter substrate;

FIG. 6 is a plan view of the arrangement of color filters disposed onthe color-filter substrate according to another embodiment;

FIG. 7 is a cross-sectional view of a liquid crystal device according tothe embodiment;

FIG. 8 is a flowchart of a method for manufacturing the liquid crystaldevice.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of the present invention will be described hereinbelowwith reference to the drawings. FIGS. 1 to 7 show an embodiment of theinvention. FIG. 1 is a front view of a color-filter substrate. FIG. 2 isa cross-sectional view of the same, taken along line II-II of FIG. 1.

Numeral 1 in the drawings denotes a color-filter substrate. Thecolor-filter substrate 1 is provided to opposing substrates of, forexample, a liquid crystal device. The color-filter substrate 1 has aplurality of color filters R, B, and G which are colored in the threeprimary colors of light, red (R), blue (B), and green (G), respectively,in a specified pattern and also has an alignment-layer application area2 thereon.

An alignment-layer material is applied to the alignment-layerapplication area 2 with a droplet discharge head 3 to form an alignmentlayer 4. The alignment-layer material applied on the color-filtersubstrate 1 and the alignment layer 4 formed by the alignment-layermaterial dried and solidified are shown in the same shape on thedrawings. Accordingly, numeral to be given to the alignment-layermaterial is omitted hereinafter for convenience.

Referring to FIG. 3, the droplet discharge head 3 which applies analignment-layer material to the surface of the color-filter substrate 1has one or multiple trains of nozzles 3 a. An alignment-layer materialheld in an ink tank (not shown) is supplied to each nozzle 3 a through asupply port 3 b.

For the alignment-layer material, the same as that used in the generalflexography, such as polyimide, is used. The viscosity and the dischargeamount of one droplet are determined in consideration of a spread whenapplied to the color-filter substrate 1. Specifically, as shown in FIG.4( a), the viscosity of the alignment-layer material and the dischargeamount of one droplet of the nozzle 3 a are set by experiment etc. sothat the alignment-layer material applied to the color-filter substrate1 is not dispersed on the color-filter substrate 1 but can be dried andsolidified at a preset thickness.

A table (not shown) for placing the color-filter substrate 1 and thedroplet discharge head 3 can make a relative movement in two dimensionaldirections (X, Y) with a controller (not shown). The alignment-layermaterial discharged from the nozzles 3 a of the droplet discharge head 3is applied to the entire alignment-layer application area 2 of thecolor-filter substrate 1 by the relative movement of the table and thedroplet discharge head 3.

In this case, when the effective discharge width WI of the nozzles 3 aof the droplet discharge head 3 is smaller than the X-directioneffective width W2 of the alignment-layer application area 2 of thecolor-filter substrate 1, as shown in FIG. 1, the droplet discharge head3 is reciprocated along preset multiple alignment-layer applicationtrains to apply the alignment-layer material onto the entirealignment-layer application area 2.

More specifically, one of the table and the droplet discharge head 3placed above the color-filter substrate 1 placed on the table, opposedthereto with a predetermined space therebetween, is moved in thedirection of arrow Y relative to the color-filter substrate 1, and thefirst alignment-layer application train of the color-filter substrate 1is scanned with the droplet discharge head 3. The droplet discharge head3 is then moved a specified pitch in the direction of arrow X relativeto the color-filter substrate 1 by the relative movement of the tableand the droplet discharge head 3, thereby scanning the secondalignment-layer application train.

The entire alignment-layer application area 2 on the color-filtersubstrate 1 is scanned by repeating that process, during which thealignment-layer material discharged from the nozzles 3 a of the dropletdischarge head 3 is applied onto the color-filter substrate 1, therebyforming the alignment layer 4 on the entire alignment-layer applicationarea 2, as shown in FIG. 2.

When the alignment-layer material is applied to a precedingalignment-layer application train and then to the followingalignment-layer application train with the droplet discharge head 3, thealignment-layer material applied to the preceding alignment-layerapplication train has been dried and solidified to form aalignment-layer train 4 a or on the way to forming the alignment-layertrain 4 a. Accordingly, in order to eliminate the boundary with thefront end (hereinafter, referred to as a lateral front end) L1 in thedirection of movement along the X-direction of the alignment-layer train4 a formed in the preceding alignment-layer application train, as shownin FIG. 4 b, when the alignment-layer material is applied to thefollowing alignment-layer application train, the rear end (hereinafter,referred to as a lateral rear end) L2 in the direction of movement alongthe X-direction of the alignment-layer material applied to the followingalignment-layer application train is overlapped with the lateral frontend L1 of the alignment-layer train 4 a applied to the precedingalignment-layer application train, thereby forming an overlapped portion4 c with an overlap width W3.

As a result, the overlapped portion 4 c (refer to FIG. 4( b)) isproduced between the lateral front end L1 of the alignment-layer train 4a formed in the preceding alignment-layer application train and thelateral rear end L2 of the alignment-layer material formed in thefollowing alignment-layer application train. The overlapped portion 4 cis different in thickness from the alignment layer of the other parts,tending to affect the pre-tilt angle of liquid crystal, which can beviewed as streak unevenness in alignment from the exterior.

Therefore, the embodiment is constructed such that when analignment-layer material is applied onto the color-filter substrate 1with the droplet discharge head 3, the relative movement of the tableand the droplet discharge head 3 is set so that the overlapped portion 4c is produced at a portion corresponding to a specific color arrangementof the three primary colors (R, B, and G) which construct a color filterto be used for a color liquid crystal device. The specific color ispreferably blue (B). Blue (B) is known to be generally lower invisibility than the other two colors (red and green) and difficult toview as luminance difference even if streak unevenness in alignmentoccurs owing to the variation in the thickness of the alignment layer 4.

Accordingly, for example, when the color filters R, B, and G arearranged such that the same colors R, B, and G are arranged inrespective columns, as shown in FIG. 5, the relative movement of thetable and the droplet discharge head 3 in the direction of the twodimensions (X, Y) is set so that the overlapped portion 4 c shown inFIG. 4(b) is formed on a portion corresponding to the train of the colorfilter B. In that case, as shown in FIG. 6, when the color filters R, B,and G are arranged to be displaced one by one, the color-filtersubstrate 1 is tilted so that the overlapped portion 4 c is formed alongthe color filter B.

This embodiment is constructed such that when the table and the dropletdischarge head 3 are reciprocated to scan the color-filter substrate 1,the overlapped portion 4 c (refer to FIG. 4 b) formed of thealignment-layer train 4 a formed on the preceding alignment-layerapplication train and the alignment-layer train 4 b formed on thefollowing alignment-layer application train passes through a partcorresponding to the color filter B which displays blue of the lowestvisibility and lowest luminance difference of the color filters R, B,and G. Accordingly, streak unevenness in alignment is difficult to seefrom the exterior, thus improving the quality of products.

The operation of the embodiment will now be described. The color-filtersubstrate 1 is first placed on the table with a specified alignment. Thecolor filters R, B, and G provided on the color-filter substrate 1 arethen arranged such that the same display colors are aligned along theY-direction which is the reciprocating scanning direction of the dropletdischarge head 3 (refer to FIGS. 6 and 7).

The droplet discharge head 3 is then moved relatively in the Y-directionalong a preset coordinate to apply an alignment-layer materialdischarged from the nozzles 3 a of the droplet discharge head 3 onto thefirst alignment-layer application train of the color-filter substrate 1,in which case the lateral front end L1 of the alignment-layer materialis set to the position of the color filter B, as shown in FIGS. 4 and 5.

After completion of the application of the alignment-layer material tothe first alignment-layer application train of the color-filtersubstrate 1, the droplet discharge head 3 is moved in the X-direction toapply the alignment-layer material to the following alignment-layerapplication train. The stroke of the droplet discharge head 3 in theX-direction for the second and following alignment-layer applicationtrains is set so that the lateral rear end L2 of the alignment-layermaterial discharged from the nozzles 3 a is overlapped with or incontact with the lateral front end L1 of the alignment-layer train 4 aformed by the preceding application. The effective discharge width W1 ofthe second and following nozzles 3 a is set so that the lateral frontend L1 is located at the position of the color filter B by controllingthe number of discharges of the nozzles 3 a.

Accordingly, the effective discharge width W1, which is set so that theends L2 and L1 of the alignment-layer material form the overlappedportion 4 c as shown in FIG. 4( b), is set to a value obtained by addingthe overlap width W3 of the overlapped portion 4 c to a valueapproximately integer times the interval of pixels, with the arrangementof the color filters R, B, and G as one unit.

The overlap width W3 of the overlapped portion 4 c varies and so is notconstant under the influence of the deflections at relativereciprocating scanning of the table and the droplet discharge head 3,the accuracy error of the effective discharge width W1 of the nozzles 3a, etc. Therefore, the effective discharge width W1 is set inconsideration of the variation factors by experiment etc. so that theoverlap width W3 of the overlapped portion 4 c is set within the widthof the color filter B at the maximum, and such that the ends L1 and L2come into contact with each other at the minimum.

Accordingly, the alignment-layer material can be applied to the entirealignment-layer application area 2 of the color-filter substrate 1 byreciprocating the droplet discharge head 3 at a specified pitch in theX-direction to scan the color-filter substrate 1. As shown in FIGS. 5and 6, the overlapped portion 4 c (refer to FIG. 4 b) of the alignmentlayer 4 is produced at a position corresponding to the color filter Bwhich displays color with the lowest visibility and lowest luminancedifference of the color filters R, B, and G disposed on the color-filtersubstrate 1.

Consequently, streak unevenness in alignment generated by the overlappedportion 4 c of the alignment layer 4 is difficult to see from theexterior, thus improving the quality of products.

It is to be understood that the present invention is not limited to theforegoing embodiment but it is also possible to form the alignment-layertrains 4 a and 4 b on the color-filter substrate 1 by flexography andrepeat it to form the alignment layer 4 on the entire alignment-layerapplication area 2 of the color-filter substrate 1.

First Embodiment

An embodiment of a liquid crystal device 11 which includes thecolor-filter substrate 1 according to the embodiment will next bedescribed. The liquid crystal device 11 according to the embodimentincludes an opposing substrate 10 and a device substrate 20 opposed toeach other. The substrates 10 and 20 are bonded together via a sealingmaterial 30 and have a liquid-crystal sealed area 35 therein. Theliquid-crystal sealed area 35 contains liquid crystal (not shown). Alight source (not shown) is disposed on the outer surface of theopposing substrate 10.

The opposing substrate 10 includes a plurality of color filters 55 (R,G, and B) colored in red (R), blue (B), and green (G), respectively, inthe area on a transparent substrate 101, such as a glass substrate,which corresponds to the intersection of a first electrode pattern 40and a second electrode pattern 50. In this embodiment, the opposingsubstrate 10 corresponds to the color-filter substrate 1 of thisembodiment.

The color filters 55 (R, B, and G) are aligned in a specified pattern onthe transparent substrate 101 (refer to FIG. 5 or 6). The firstelectrode pattern 40 and the alignment layer 4 are formed in order onthe surface of the color filters 55 (R, B, and G). Both of the firstelectrode pattern 40 and the second electrode pattern 50 are made of atransparent conducting layer, typified by indium tin oxide (ITO). Alight shielding layer 16 is formed at the boundary of the color filters55 (R, B, and G).

The second electrode pattern 50, an overcoat layer 29, and the alignmentlayer 4 are formed in order on a transparent substrate 201, such as aglass substrate, which constructs the device substrate 20.

The alignment layer 4 is formed on the color filters 55 (R, B, and G)and the overcoat layer 29 by the droplet discharge method according tothe embodiment.

The alignment layer 4 formed by the droplet discharge method of thisembodiment has the overlapped portion 4 c at which the ends L1 and L2 ofthe adjacent alignment-layer train 4 a and 4 b are overlapped with eachother, at a position corresponding to the color filter 55(B).

Blue which is displayed by the color filter 55(B) has lower visibilityand lower luminance difference than colors (R and G) displayed with theother color filters 55 (R and G). Accordingly, when the overlappedportion 4 c is disposed at a position corresponding to the color filter55(B), streak unevenness in alignment generated by the overlappedportion 4 c is difficult to see from the exterior, thus improving thequality of products.

Referring now to the flowchart of FIG. 8, a method for manufacturing theliquid crystal device 11 according to the embodiment will be described.In manufacturing the liquid crystal device 11, the electrode patterns 40and 50 are formed with a semiconductor process, with the opposingsubstrate 10 and the device substrate 20 in the state of largesubstrates (not shown) from which a large number of substrates can betaken.

More specifically, a large substrate (not shown) is subjected to stepST11 of forming the light shielding layer 16, step ST12 of forming thecolor filters 55, step S13 of forming the electrode pattern 40, stepST14 of forming the alignment layer 4, rubbing step ST15, and step ST16of applying the sealing material 30, in the state of a large substratefrom which a large number of transparent substrates 101 can be taken.

Then, a large substrate (not shown) is subjected to step ST21 of formingthe electrode pattern 50, step ST22 of forming the overcoat layer 29,step ST23 of forming the alignment layer 4, rubbing step ST24, and stepST25 of spraying a gap material, in the state of a large substrate fromwhich a large number of transparent substrates 201 can be taken.

In bonding step ST31, both the large substrates (not shown) beforedivided to multiple opposing substrates 10 and device substrates 20 arebonded together to form a large panel structure and then it is cut tostrip panel structures in first breaking step ST32.

In liquid-crystal charging and sealing step ST33, after theliquid-crystal sealed area 35 (refer to FIG. 7) formed in the strippanel structure is filled with liquid crystal and then sealed.Subsequently, in second breaking step ST34, the strip panel structure iscut into the liquid crystal devices 11 and then, in mounting step ST35,a flexible substrate etc. are mounted to each liquid crystal device 11.

In step ST14 of forming the alignment layer 4, the alignment-layertrains 4 a and 4 b are formed on every train by the droplet dischargemethod to form the alignment layer 4 on the entire alignment-layerapplication area 2 finally. The overlapped portion 4 c formed at theadjacent ends L1 and L2 is formed on the color filter 55(B), so thatstreak unevenness in alignment generated by the overlapped portion 4 cis difficult to see from the exterior, thus improving the quality of theproducts.

Although the embodiment has been described for the alignment layer 4formed on the opposing substrate 10, the alignment layer 4 formed on thedevice substrate 20 has also the same structure. Specifically, in stepST23 of forming the alignment layer 4 on the transparent substrate 201of the device substrate 20, the overlapped portion 4 c of thealignment-layer trains 4 a and 4 b is formed at a position correspondingto the color filter 55(B) (the position directly below the color filter55(B) shown in FIG. 7), as in step ST14 of forming the alignment layer 4on the opposing substrate 10. Since the overlapped portion 4 c of thealignment-layer trains 4 a and 4 b is formed directly below the colorfilter 55(B), also the streak unevenness in alignment generated by theoverlapped portion 4 c is difficult to see from the exterior.

1. An apparatus for manufacturing a color-filter substrate, comprising:a table for placing a substrate having a plurality of color filters; adroplet discharge head opposed to the substrate and capable of relativemovement in two-dimensional directions along the substrate; and acontroller specifically programmed to control the two-dimensionalrelative movement of the table and the droplet discharge head so that: alateral front end of a first application of the alignment-layer materialdischarged from nozzles provided to the droplet discharge head islocated at a position corresponding to a color filter of a specificcolor; and a lateral rear end of a second application of thealignment-layer material discharged from the nozzles provided to thedroplet discharge head overlaps with the lateral front end of the firstapplication of the alignment-layer material.
 2. The apparatus formanufacturing a color-filter substrate according to claim 1, wherein thespecific color is blue.